/* Web3 Course — light theme, dense, SWE-friendly */
:root {
  --bg: #fbfaf7;
  --bg-alt: #ffffff;
  --ink: #1a1a1a;
  --muted: #5b6472;
  --line: #e4e2dc;
  --brand: #2b5df5;
  --brand-ink: #1b44c2;
  --accent: #d46a00;
  --ok: #0c8a3e;
  --warn: #b3261e;
  --code-bg: #0f1222;
  --code-ink: #e6e8ff;
  --yellow: #fff6d6;
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Inter, Roboto, sans-serif;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  background: var(--bg);
  color: var(--ink);
  font-family: var(--sans);
  line-height: 1.55;
  font-size: 16px;
}

a { color: var(--brand-ink); text-decoration: none; }
a:hover { text-decoration: underline; }

/* Layout */
.wrap { max-width: 960px; margin: 0 auto; padding: 24px 20px 80px; }
.top {
  position: sticky; top: 0; z-index: 10;
  background: rgba(251,250,247,0.92);
  backdrop-filter: saturate(150%) blur(6px);
  border-bottom: 1px solid var(--line);
}
.top-inner {
  max-width: 960px; margin: 0 auto;
  display: flex; align-items: center; gap: 16px;
  padding: 10px 20px;
}
.top .brand { font-weight: 700; letter-spacing: .2px; }
.top .brand .dot { color: var(--brand); }
.top nav { margin-left: auto; display: flex; gap: 14px; flex-wrap: wrap; font-size: 14px; }
.top nav a { color: var(--muted); }
.top nav a.active, .top nav a:hover { color: var(--ink); }

h1 { font-size: 30px; margin: 10px 0 6px; letter-spacing: -0.01em; }
h2 { font-size: 22px; margin: 28px 0 8px; }
h3 { font-size: 17px; margin: 20px 0 6px; }
p { margin: 8px 0; }
.lede { color: var(--muted); font-size: 15px; }

/* Phase cards on index */
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); gap: 14px; margin-top: 14px; }
.card {
  background: var(--bg-alt); border: 1px solid var(--line); border-radius: 10px;
  padding: 14px 16px; transition: transform .08s ease, box-shadow .08s ease;
}
.card:hover { transform: translateY(-1px); box-shadow: 0 3px 12px rgba(0,0,0,.05); }
.card .num { font-family: var(--mono); color: var(--brand); font-size: 12px; letter-spacing: .05em; }
.card h3 { margin: 4px 0 4px; font-size: 16px; }
.card p { margin: 0; color: var(--muted); font-size: 13.5px; }

/* Callouts */
.note, .warn, .tip, .analogy, .goal {
  border: 1px solid var(--line); border-left: 4px solid var(--brand);
  background: var(--bg-alt); padding: 10px 14px; border-radius: 6px; margin: 12px 0;
}
.warn { border-left-color: var(--warn); background: #fff5f4; }
.tip { border-left-color: var(--ok); background: #f3faf5; }
.analogy { border-left-color: var(--accent); background: #fff6ea; }
.goal { border-left-color: #6b46c1; background: #f7f2ff; }
.note b, .warn b, .tip b, .analogy b, .goal b { text-transform: uppercase; font-size: 12px; letter-spacing: .08em; }
.analogy b { color: var(--accent); }
.tip b { color: var(--ok); }
.warn b { color: var(--warn); }
.goal b { color: #6b46c1; }
.note b { color: var(--brand-ink); }

/* Code */
pre, code { font-family: var(--mono); }
pre {
  background: var(--code-bg); color: var(--code-ink);
  padding: 12px 14px; border-radius: 8px; overflow-x: auto;
  font-size: 13.2px; line-height: 1.5;
}
code.inline, p code, li code, td code { background: #eee9d9; color: #5a3b00; padding: 1px 5px; border-radius: 4px; font-size: 13px; }
pre code { background: transparent; color: inherit; padding: 0; font-size: inherit; }

/* Tables */
table { width: 100%; border-collapse: collapse; margin: 10px 0; font-size: 14px; }
th, td { border: 1px solid var(--line); padding: 8px 10px; text-align: left; vertical-align: top; }
th { background: #f4f1e8; font-weight: 600; }

/* Tabs */
.tabs { display: flex; gap: 2px; border-bottom: 1px solid var(--line); margin-top: 12px; }
.tabs button {
  background: transparent; border: 1px solid var(--line); border-bottom: none;
  padding: 6px 12px; cursor: pointer; font-family: var(--sans); font-size: 14px;
  border-radius: 6px 6px 0 0; color: var(--muted);
}
.tabs button.active { background: var(--bg-alt); color: var(--ink); border-color: var(--line); }
.tab-body { border: 1px solid var(--line); border-top: none; padding: 12px 14px; background: var(--bg-alt); border-radius: 0 6px 6px 6px; }
.tab-body > div { display: none; }
.tab-body > div.active { display: block; }

/* Details */
details { border: 1px solid var(--line); border-radius: 6px; padding: 8px 12px; margin: 8px 0; background: var(--bg-alt); }
details summary { cursor: pointer; font-weight: 600; }
details[open] summary { margin-bottom: 6px; }

/* Quiz */
.quiz { background: var(--yellow); border: 1px solid #e7d38a; border-radius: 8px; padding: 12px 14px; margin: 14px 0; }
.quiz .q { font-weight: 600; }
.quiz ul { list-style: none; padding: 0; margin: 8px 0 0; }
.quiz li { padding: 6px 8px; border-radius: 4px; cursor: pointer; border: 1px solid transparent; }
.quiz li:hover { background: #fdeab3; }
.quiz li.correct { background: #d3f4df; border-color: #79c798; }
.quiz li.wrong { background: #f9d3cf; border-color: #e08b82; }
.quiz .explain { display: none; margin-top: 8px; font-size: 14px; color: #4d4a3a; }
.quiz.answered .explain { display: block; }

/* Nav prev/next */
.pager { display: flex; justify-content: space-between; margin-top: 40px; padding-top: 16px; border-top: 1px solid var(--line); font-size: 14px; }
.pager a { padding: 8px 14px; border: 1px solid var(--line); border-radius: 6px; background: var(--bg-alt); }
.pager a:hover { border-color: var(--brand); text-decoration: none; }
.pager span.muted { color: var(--muted); }

/* TOC */
.toc { background: var(--bg-alt); border: 1px solid var(--line); padding: 10px 16px; border-radius: 8px; margin: 12px 0 20px; font-size: 14px; }
.toc ol { margin: 4px 0 0 18px; padding: 0; }
.toc a { color: var(--ink); }

/* Pill tags */
.tag { display: inline-block; font-size: 11px; padding: 2px 8px; border-radius: 20px; background: #eef1ff; color: var(--brand-ink); margin-right: 6px; font-family: var(--mono); }
.tag.red { background: #fde7e4; color: var(--warn); }
.tag.green { background: #e2f5ea; color: var(--ok); }
.tag.amber { background: #fff1d1; color: #8a5a00; }

/* Hero meta */
.meta { color: var(--muted); font-size: 13px; margin-bottom: 8px; }
.meta .sep { margin: 0 6px; }

hr { border: none; border-top: 1px solid var(--line); margin: 24px 0; }

/* Small helpers */
.mono { font-family: var(--mono); }
.small { font-size: 13px; color: var(--muted); }
.kbd { font-family: var(--mono); background: #eee; border: 1px solid #ccc; border-bottom-width: 2px; padding: 1px 5px; border-radius: 4px; font-size: 12px; }

/* Diagram */
.diagram { background: var(--bg-alt); border: 1px dashed var(--line); border-radius: 8px; padding: 12px; font-family: var(--mono); font-size: 12.5px; white-space: pre; overflow-x: auto; color: #333; }